( informal ) used to say that you do not know the answer to sth :
'Why did she say that?' 'Lord knows!'
( informal ) used to say that you do not know the answer to sth :
'Why did she say that?' 'Lord knows!'
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005